The present invention relates generally to turbomachines and more particularly to vane and blade assemblies utilized in the high pressure turbine section of gas turbine engines.
It is desirable to operate a gas turbine engine at high temperatures most efficient for generating and extracting energy from the combustion gases. Certain components of the gas turbine engine, for example, stationary vane segments of a turbine stator assembly which closely surround the turbine rotor and which define the outer boundary for the hot combustion gases flowing through the turbine, are directly exposed to the heated stream of combustion gases. The vane segments typically incorporate one, two or more individual vanes or airfoils extending between inner and outer bands or shrouds.
It has been determined that there is the potential for significant increases in temperature on the sidewalls of the vane segments, due to a lack of cooling air sweeping over the intersegment gap between two adjacent vane segments. Instead of cooling air, hot combustion gas is forced into the “chute” above the intersegment seal in the gap between adjacent vane segments. The combustion gas heats the edges of the vane segment inner (or outer) shroud or band on two faces i.e., the forward edge of the segment and an adjacent side edge. The most problematic is the vane segment side edge, or slashface, closest to the leading edge of one of the vane segment airfoils, where combustion gas pressure is highest. The concentrated heat load can potentially result in oxidation, cracking and burning, often resulting in irreparable damage to the nozzle or vane segment.
The current accepted solution to this problem is to pressurize the entire nozzle diaphragm so as to force enough cooling air into the chute region to purge any resident hot gases. This option, however, significantly degrades performance of the turbine engine due to the diversion of relatively large amounts of compressor discharge air to pressurize the nozzle diaphragm.
There remains a need, therefore, for a solution that does not degrade turbine engine performance, and which is comparatively simple and less expensive than current solutions.